Forced air heater including on-board source of electric energy

ABSTRACT

A forced-air heater having a self-contained on-board electric-power supply, a fuel tank, a support, a housing, a combustion chamber, and a motorized fan. The self-contained on-board electric-power supply may have a generator, a photovoltaic component, or some combination thereof. The fuel tank may be adapted to store a first fuel. The combustion chamber may be adapted to generate heat by combusting the first fuel with air. The motorized fan may be adapted to draw in ambient air through an air intake and force the air into the combustion chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. application Ser. No.13/182,713, filed Jul. 14, 2011, which claims the benefit of and is acontinuation of U.S. application Ser. No. 11/954,704, filed Dec. 12,2007, which has issued as U.S. Pat. No. 8,068,724, and which claims thebenefit of U.S. Provisional Application No. 60/874,427, filed Dec. 12,2006. All of the subject matter disclosed by U.S. Ser. No. 60/874,427 ishereby incorporated by reference into this application. All of thesubject matter disclosed by U.S. Ser. No. 11/954,704 is herebyincorporated by reference into this application. All of the subjectmatter disclosed by U.S. Ser. No. 13/182,713 is hereby incorporated byreference into this application.

BACKGROUND

This matter relates generally to portable forced-air heaters, and moreparticularly to portable forced-air heaters that derive at least aportion of their electric energy required for operation of the heaters,or an accessory thereof, from an on board source.

Fuel-fired portable heaters such as forced-air heaters find use inmultiple environments. The heater typically includes a cylindricalhousing with a combustion chamber disposed coaxially therein. Acombustible liquid fuel from a fuel tank is atomized and mixed with airinside the combustion chamber where it is combusted, resulting in thegeneration of a flame. During combustion of the air/fuel mixture a fanblade is rotated by an electric motor to draw ambient air into theheater to be heated by the combustion of the air/fuel mixture. Theheated air is expelled out of the heater by the continuous influx of aircaused by the fan.

Traditionally, forced-air heaters have required a source of electricenergy to energize the motor that rotates the fan blade and optionallyto operate an ignition source that triggers combustion of the air/fuelmixture. The fan is often a heavy-duty, high output fan that consumessignificant amounts of electric energy during operation thereof, andoperation of the igniter consumes even more electric energy. The demandfor electric energy created by operation of the fan and other electriccomponents of forced-air heaters has required such heaters to be pluggedinto a conventional wall outlet supplying alternating current (“AC”)electric energy generated by a public utility. In remote environments alengthy extension cord can establish a conductive pathway for theelectric energy between a wall outlet and the location of the forced-airheater. However, at locations where a new structure is being built aconventional wall outlet is typically not available, requiring the useof a portable generator to supply the electric energy untilutility-generated electric energy becomes available.

As previously mentioned, forced-air heaters are often utilized toprovide heat to new construction environments for significant periods oftime that can extend well into the night. After dusk, illumination ofthe environment in the vicinity of the forced-air heater is required toenable workers to view their worksite and avoid potentially hazardousconditions. Assuming that a conventional wall outlet is available, anextension cord can be used to conduct electric energy from the walloutlet to an on-site light stand. However, the light stand adds to theequipment that must be transported to a jobsite, and a conventional walloutlet is usually not available during the initial stages of a newconstruction.

Even in instances when a conventional wall outlet is available, thereare normally a limited number of electric devices that can be powered bythe outlet at any given time. Using adaptors to increase the number ofavailable outlets into which an electrical device can be plugged canlead to excessive currents being drawn through an extension cord orother adaptor. Thus, there are a limited number of electrical devicesthat can be simultaneously powered on a new construction jobsite at anygiven time. This limitation is even greater when a wall outlet supplyingutility-generated electricity is unavailable.

Forced-air heaters are also relatively bulky, and occupy a significantamount of storage space while not in use. Attempts to store such aheater in an alternative orientation other than its intended operationalorientation in which the heater is designed to be fired in order toconserve storage space results in the liquid fuel leaking out of theheater. And although the fuel can be drained from the heater beforestoring it in an alternative orientation to minimize the leakage offuel, such an option is time consuming, and is impractical for temporarystorage on a daily basis.

Accordingly, there remains a need in the art for a forced air heaterthat is operational in a remote environment in the absence of aconventional wall outlet or other external supply of electric energy.

SUMMARY

Provided is a forced-air heater having a self-contained on-boardelectric-power supply, a fuel tank, a support, a housing, a combustionchamber, and a motorized fan. The self-contained on-board electric-powersupply may have a generator, a photovoltaic component, or somecombination thereof. The fuel tank may be adapted to store a first fuel.The combustion chamber may be adapted to generate heat by combusting thefirst fuel with air. The motorized fan may be adapted to draw in ambientair through an air intake and force the air into the combustion chamber.

Also provided is a method for producing heat including providing aforced-air heater, generating electric power from the self-containedon-board electric-power supply, and directing a majority of thegenerated electric power to an electric load component or externalelectric load accessory other than a resistive heating element. Theforced-air heater may have a self-contained on-board electric-powersupply, a fuel tank adapted to store a first fuel, a support, a housing,a combustion chamber adapted to generate heat by combusting the firstfuel with air, and a motorized fan adapted to operate to draw in ambientair through an air intake, and force the air into the combustionchamber.

Also provided is a forced-air heater having a self-contained on-boardelectric-power supply having a generator, a fuel tank adapted to store afirst fuel, said first fuel comprising fuel oil, kerosene, gasoline, oralcohol, a support, a housing, a battery having a lithium ion battery ora sealed lead-acid battery, an engine operationally engaged with thegenerator, a combustion chamber adapted to generate heat by combustingthe first fuel with air, and a motorized fan adapted to operate to drawin ambient air through an air intake and force air into the combustionchamber. The engine may be an internal combustion engine adapted togenerate work from combustion of a second fuel other than the firstfuel.

BRIEF DESCRIPTION OF THE DRAWINGS

The present subject matter may take physical form in certain parts andarrangement of parts, embodiments of which will be described in detailin this specification and illustrated in the accompanying drawings whichform a part hereof, and wherein:

FIG. 1 is a perspective view of a forced-air heater including an outletand a light exposed to an exterior of the forced-air heater inaccordance with an embodiment of the present subject matter;

FIG. 2 is a perspective view of a forced-air heater including an outletand a light exposed to an exterior of the forced-air heater inaccordance with an embodiment of the present subject matter;

FIG. 3 is a cutaway view of a forced-air heater in accordance with anembodiment of the present subject matter;

FIG. 3A is a cutaway view of a forced-air heater in accordance with anembodiment of the present subject matter;

FIG. 3B is a cutaway view of a forced-air heater in accordance with anembodiment of the present subject matter;

FIG. 4 is a cutaway view of a battery that can optionally be utilized asa power source for a forced-air heater in accordance with the presentsubject matter;

FIG. 5 is a view of a forced-air heater in an orientation in which it isto be fired according to an embodiment of the present subject matter;

FIG. 6 is a view of a forced-air heater in an orientation in which itcan optionally be transported with minimal leakage of a liquid fuel fromthe heater's fuel tank according to an embodiment of the present subjectmatter;

FIG. 7 is a view of a forced-air heater in a substantially-verticalorientation in which it can optionally be stored with minimal leakage ofa liquid fuel from the heater's fuel tank according to an embodiment ofthe present subject matter; and

FIG. 8 is a cutaway view of a fuel management system that can optionallybe provided to a forced-air heater according to an embodiment of thepresent subject matter.

DETAILED DESCRIPTION

Certain terminology is used herein for convenience only and is not to betaken as a limitation on the present subject matter. Relative languageused herein is best understood with reference to the drawings, in whichlike numerals are used to identify like or similar items. Further, inthe drawings, certain features may be shown in somewhat schematic form.

FIGS. 1 and 2 show illustrative embodiments of a forced-air heater 1,which generally includes a fuel tank 3, a support 5, a housing includingupper and lower housing portions 8, 7, respectively, and a combustionchamber 10 including an inner cylinder (not shown) and an outer cylinder12. Alternate embodiments include a housing formed as a singular,generally cylindrical shell. A semi-spherical shaped baffle 13 isprovided adjacent to a discharge end 2 of the combustion chamber 10 andan intake guard 14 is provided adjacent to an air intake end 19 port ofthe forced-air heater 1.

The fuel tank 3 can optionally be formed as a singular molded unit orfrom two opposing rectangular trays arranged with their openings facingeach other. For embodiments including a fuel tank 3 formed from twoopposing trays, the trays are joined together by seam welding orotherwise coupling flanges 3 a extending around the perimeter of thefuel tank 3. A removable filler cap 4 covers a fueling aperture (notshown) formed in a surface of the fuel tank 3 through which a liquidfuel 20 (FIG. 3) such as diesel fuel oil, another suitable grade fueloil, kerosene, gasoline, alcohol, or the like may be added. The liquidfuel is atomized and combined with air or other oxygen source in thecombustion chamber 10, where it is combusted to generate the thermalenergy for heating air being forced through the forced-air heater 1.

The combustion chamber 10 includes a cavity defined by a generallycylindrical shell 12. An annular space 71 (FIG. 3) is left between anouter surface of the shell 12 and the housing to reduce the amount ofheat that is transferred therebetween from the amount of heat that wouldbe so transferred if the outer surface of the shell 12 contacted thehousing. The combustion chamber 10 is secured to the housing by aplurality of brackets disposed about the periphery of the combustionchamber's input and output. The brackets are secured by screws or thelike to the shell 12 and to locations of the housing. One or morebrackets are also provided to couple the baffle 13 to the shell 12defining the combustion chamber 10.

A light 38 can optionally be coupled to the heater 1 to illuminate anenvironment within the vicinity of the heater 1. The light 38 can be anyconventional electric light including, but not limited to a fluorescentlight, incandescent light, high-intensity light emitting diode (“LED”),and the like. A clear, translucent, colored, or slightly opaqueprotective shroud or lens can optionally be provided to protect thelight 38 from being damaged by other objects near the heater 1. Further,operation of the light 38 can be controlled by the operator with aswitch 42 independent of the operation of the other components of theforced-air heater 1 and the combustion of fuel from the fuel tank 3. Theswitch 42 can be any type of operator input device, such as amulti-position switch, one or more push button switches (as shown inFIGS. 1 and 2), and the like. In FIGS. 1 and 2, the switch 42 includesan ON pushbutton switch 42 a and an OFF pushbutton switch 42 b, whichturn the light 38 on and off, respectively. According to alternateembodiments, the switch 42 can optionally offer a plurality of intensitysettings, such as low, medium and high, or can be controlled with aninfinitely adjustable dimmer switch to control the intensity of thelight 42.

A heater control panel 46 is operatively coupled to the heater 1 toallow the operator to control heating of the ambient environment by theheater 1. The control panel 46 in the illustrative embodiments shown inFIGS. 1 and 2 include a thermostat interface 48 and an ignition switch52. The thermostat interface 48 can be rotated about a central axis to adesired temperature to which the operator wishes to heat the ambientenvironment of the heater 1. The thermostat interface 48 can beinfinitely adjusted between high and low temperature limits, or can berotated to one or more predetermined temperature settings such as LOW,MEDIUM and HIGH. The temperature selected with the thermostat interface48 can govern operation of an electric motor 15 discussed below,ignition of an air/fuel mixture, the supply of fuel to the combustionchamber 10, the ratio of air to fuel provided to the combustion chamber10, an igniter 56 discussed below with reference to FIG. 3, or anycombination thereof. As is known in the art, a thermostat operativelycoupled to the thermostat interface 48 controls activation,deactivation, and operation of any of these components to maintain thetemperature within the ambient environment of the heater 1 atapproximately the temperature selected with the thermostat interface 48.

The support 5 is secured to or otherwise formed adjacent to the topsurface of the fuel tank 3 by spot welding, brazing, or the like, andsupports the heater's housing. The support 5 includes at least oneadjustable panel 6 that can be adjusted by an operator to gain accessinto an interior chamber 21 defined by the support 5. The adjustablepanel 6 can be secured to the support 5 by any type of fastener thatpermits adjustment of the adjustable panel 6 to allow access into theinterior chamber 21. Examples of such fasteners include a hinge, lockingscrew, latch, and the like. The interior chamber can house components ofthe forced-air heater 1, such as a self-contained, on-board power supply24 (FIG. 3), control and ignition circuitry, electrical wiring, air andfuel hoses, and the like. Each of such components can be serviced,replaced or accessed through the aperture in the support 5 concealed bythe adjustable panel 6 is removable to provide convenient access to thecomponents housed in the compartment for servicing and replacement.

The self-contained, on-board power supply 24 can be any type of portableenergy source that can supply electric energy, at least temporarily,when utility-generated electric energy is unavailable. Examples ofsuitable on-board power supplies 24 include, but are not limited to, abattery, a thermoelectric component, a generator, a fuel cell, aphotovoltaic component, an ultracapacitor, some combination thereof, andthe like.

In embodiments in which the power supply 24 comprises a battery, thebattery may comprise a zinc-carbon battery, a zinc-chloride battery, analkaline battery, a nickel oxyhydroxide battery, a lithium battery, amercury oxide battery, a zinc-air battery, a silver-oxide battery, anickel-cadmium battery, a lead-acid battery, a nickel-metal hydridebattery, a nickel-zinc battery, a lithium ion battery, or somecombination thereof. In certain embodiments, a battery may be sealed,such as, without limitation, a sealed lead-acid battery.

An example of a suitable battery is the lithium secondary cell battery(also called a lithium ion battery), a cutaway view of which is shownschematically in FIG. 4. Details of such a battery are disclosed inUnited States Patent Publication No. US 2005/0233219, published on Oct.20, 2005, which is incorporated in its entirety herein by reference.Another example of a suitable battery 24 is described in detail inUnited States Publication No. US 2005/0233220, published on Oct. 20,2005, which is also incorporated in its entirety herein by reference.This, or batteries with similar performance characteristics may beutilized to supply electric energy, at least temporarily, to one or moreelectric components of the forced-air heater 1.

The aforementioned lithium ion examples of a suitable battery that canbe used as the power source 24 of the present subject matter include ahigh-capacity lithium-containing positive electrode in electroniccontact with a positive electrode current collector. A high-capacitynegative electrode is in electronic contact with a negative electrodecollector. The positive and negative collectors are in electricalcontact with separate external circuits. A separator is positioned inionic contact between with the cathode (positive terminal) and the anode(negative terminal), and an electrolyte is in ionic contact with thepositive and negative electrodes. The slow discharge rates of thebattery allow for extended shelf-life and extended use characteristics.

The total and relative area specific impedances for the positive andnegative electrodes of such exemplary batteries 24 are such that thenegative electrode potential is above the potential of metallic lithiumduring charging at greater than or equal to 4C (4 times the ratedcapacity of the battery per hour). The current capacity per unit area ofthe positive and negative electrodes each are at least 3 mA-h/cm2 andthe total area specific impedance for the cell is less than about 20Ω-cm2. The ratio of the area specific impedances of the positiveelectrode to the negative electrode is at least about ten.

Also, for the lithium ion batteries 24 discussed in the examples above,the area specific impedance of the total cell is localized predominantlyat the positive electrode. The charge capacity per unit area of thepositive and negative electrodes each are preferably at least 0.75mA-h/cm2, more preferably at least 1.0 mA-h/cm2, and most preferably atleast 1.5 mA-h/cm2. The total area specific impedance for the cell isless than about 16 Ω-cm2, preferably less than about 14 Ω-cm2, and morepreferably less than about 12 Ω-cm2, more preferably less than about 10Ω-cm2, and most preferably less than or equal to about 3 Ω-cm2. Thenegative electrode has an area specific impedance of less than or equalto about 2.5 Ω-cm2, more preferably less than or equal to about 2.0Ω-cm2, and most preferably less than or equal to about 1.5 Ω-cm2.

Examples of suitable materials for the positive electrode include alithium transition metal phosphate including one or more of vanadium,chromium, manganese, iron, cobalt, and nickel. Examples of suitablenegative electrode materials include carbon, such as graphitic carbon.The carbon is selected from the group consisting of graphite, spheroidalgraphite, mesocarbon microbeads and carbon fibers.

Embodiments of the battery 24 can optionally include a battery elementhaving an elongated cathode and an elongated anode, which are separatedby two layers of an elongated microporous separator which are tightlywound together and placed in a battery can. An example of a typicalspiral electrode secondary cell is shown in FIG. 4, the details of whichare discussed in U.S. Patent Publication 2005/0233219 and U.S. Pat. No.6,277,522, both of which are incorporated in their entirety herein byreference. The secondary cell 200 includes a double layer of anodematerial 220 coated onto both sides of an anode collector 240, aseparator 260 and a double layer of cathode material 280 coated ontoboth sides of cathode collector 300 that have been stacked in this orderand wound to make a spiral form. The spirally wound cell is insertedinto a battery can 320 and insulating plates 340 are disposed at upperand lower surfaces of the spirally wound cell. A cathode lead 360 fromanode collector 300 provides electrical contact with the cover. An anodelead 380 is connected to the battery can 320. An electrolytic solutionis also added to the can.

FIG. 3 is a cutaway view of a forced-air heater 1 in accordance with oneembodiment of the present subject matter. Adjacent to the intake end 19of the forced-air heater 1, a motor 15 is supported by means of abracket 32 that extends between the lower and upper housing portions 7,8. A drive shaft 16 extends from and is rotationally driven by the motor15. An end of the drive shaft 16 is coupled to fan blades 18, which drawambient air in the direction of arrows 34 through the air intake end 19of the forced-air heater 1. The fan blades 18 force air into thecombustion chamber 10, where it is mixed with the atomized fuel injectedinto the combustion chamber 10 through the nozzle 36 and the mixture iscombusted. The intake guard 14 at the intake port prevents largeobjects, which can damage the fan blades 18 or block the air passages,from entering the forced-air heater 1.

The battery or other type of power supply 24 can supply electric energy,at least temporarily, to operate an electric load component of theheater 1 while the heater 1 is generating thermal energy for heating itsambient environment 35. An electric load component may comprise aresistive heating element, a component other than a resistive heatingelement such as, without limitation, a light 38, a motor 15, a controlunit 62, a rectifier 58, a fuel pump (not shown), an inverter 66, abattery, an ultracapacitor, and igniter 56 or ignition circuitry, orsome combination thereof. Electric energy can be supplied by the powersource 24 to a control unit 62 or other electric load component via anelectrical conductor 64 disposed within the internal chamber 21 of thesupport 5. The control unit 62 is operatively coupled to the operatorinterface devices provided to the heater 1 such as the switch 42,control panel 46, any other operator input device, or any combinationthereof to carry out control commands input by an operator. The controlunit 62 may include useful electrical and electronic hardware, software,or a combination thereof chosen with sound engineering judgment torespond to commands input by an operator via one or more operatorinterface devices provided to the heater 1.

The heater 1 can be equipped with a rectifier 58 that convertsalternating current (“AC”) electric energy from an external sourceconducted via a plug 28 into direct current (“DC”) electric energy. Therectifier 58 may be operatively coupled to the power supply 24 and thecontrol unit 62 to distribute DC electric energy as needed for properoperation of the heater 1. DC electric energy can be selectivelysupplied by the rectifier 58 to the control unit 62, to recharge thebattery or other power source 24, or simultaneously to the control unit62 and the power source 24 when electric energy from an external sourcesuch as a conventional wall outlet or external generator is available.Thus, when AC electric energy is available from an external source, theAC electric energy may be rectified by the rectifier 58 into DC electricenergy. In certain embodiments, if a power source 24 is chargable and ischarged to a degree that is less than a predetermined lower limit, suchas 90%, the rectifier may be adapted to automatically (i.e., withoutoperator intervention) supply DC electric energy for charging the powersource 24 until a predetermined cutoff condition is met. Simultaneously,the rectifier 58 can supply DC electric energy to the control unit 62during operation of the heater 1. In turn, the control unit 62selectively establishes conductive pathways between one or more electricload components, such as an igniter 56, light 38, fuel pump (not shown),and motor 15 for example, to energize the appropriate component(s) inresponse to control commands input by the operator via switch, 42,control panel 46 and the like.

As used herein, unless otherwise noted, a thermoelectric component mayrefer to a thermoelectric cell, a thermopile, a Peltier cell, or anyother device adapted to produce electrical energy from thermal energy.As shown in FIG. 3A, a thermoelectric component 32 may be engaged withthe heater 1 in such a way to expose part of the thermoelectriccomponent 32 to a heat source 33 and part of the thermoelectricgenerator 32 to a cold sink 35. As shown in FIG. 3A, heat source 33 maybe heater 1, and cold sink 35 may be the environment surrounding theheater 1. Thermoelectric component 32 may be utilized to supply electricenergy, at least temporarily, to one or more electric load components ofthe forced-air heater 1. Thermoelectric component 32 may be utilized tosupply electric energy for the same purposes and in a similar way to theabove-described battery or other type of power supply 24. Thermoelectriccomponent 32 may be utilized to supply electric energy, in addition toor in substitution for electric energy from a battery, generator 43,photovoltaic component 39 or other type of power supply 24. As shown inFIG. 3A, an electrical conductor 64 may electrically connectthermoelectric component 32 to control unit 62. In certain otherembodiments, thermoelectric component 32 may be in direct electricalengagement with other components of heater 1. Other means forelectrically connecting thermoelectric component 32 to heater 1 selectedwith good engineering judgment may also be acceptable.

As used herein, unless otherwise noted, a photovoltaic component mayrefer to a photovoltaic cell, a photovoltaic system, or any other deviceadapted to converts the energy of light directly into electricity by thephotovoltaic effect. As shown in FIG. 2, a photovoltaic component 39 maybe engaged with the heater 1 in such a way to expose part of thephotovoltaic component 39 to light 49. As shown in FIG. 2, light 49 maybe light, such as without limitation, sunlight, from the environmentsurrounding the heater 1. Photovoltaic component 39 may be utilized tosupply electric energy, at least temporarily, to one or more electricload components of the forced-air heater 1. Photovoltaic component 39may be utilized to supply electric energy for the same purposes and in asimilar way to the above-described battery or other type of power supply24. Photovoltaic component 39 may be utilized to supply electric energy,in addition to or in substitution for electric energy from a battery,generator 43, thermoelectric component 32, or other type of power supply24. An electrical conductor 64 may electrically connect photovoltaiccomponent 39 to control unit 62. In certain other embodiments,photovoltaic component 39 may be in direct electrical engagement withother components of heater 1. Other means for electrically connectingphotovoltaic component 39 to heater 1 selected with good engineeringjudgment may also be acceptable.

As used herein, unless otherwise noted, a generator, may refer to a DCgenerator, an AC generator, an alternator, a dynamo, or any other deviceadapted to produce electrical energy from mechanical work. As shown inFIG. 3B, a generator 43 may be engaged with the heater 1 in such a wayto receive mechanical work, directly or indirectly, from a source ofmechanical work, such as, without limitation, an engine 44 and to outputelectrical energy to the heater 1. As shown in FIG. 3B, mechanical workmay be input to the generator 43 by an input shaft 47 in the form ofshaft work. Other means for supplying mechanical work to the generator43 selected with good engineering judgment may also be acceptable.Generator 43 may be utilized to supply electric energy, at leasttemporarily, to one or more electric load components of the forced-airheater 1. Generator 43 may be utilized to supply electric energy for thesame purposes and in a similar way to the above-described battery orother type of power supply 24. Generator 43 may be utilized to supplyelectric energy, in addition to or in substitution for electric energyfrom a battery, thermoelectric component 32, photovoltaic component 39,or other type of power supply 24. Electrical energy may be output to theheater 1 via an electrical conductor 64. As shown in FIG. 3B, anelectrical conductor 64 may electrically connect generator 43 to controlunit 62. In certain other embodiments, generator 43 may be in directelectrical engagement with other components of heater 1. Other means forelectrically connecting generator 43 to heater 1 selected with goodengineering judgment may also be acceptable.

As noted above, and as shown in FIG. 3B, a generator 43 may beoperationally engaged with an engine 44 so that the engine 44 maysupply, directly or indirectly, mechanical work to the generator 43. InFIG. 3B, the engagement of engine 44 to generator 43 to transmitmechanical work thereto is by input shaft 47. In certain otherembodiments, the engagement of engine 44 to transmit mechanical work togenerator 43 may be made indirectly through a clutch, a transmission, orother components selected with good engineering judgment. Engine 44 maybe an internal combustion engine or an external combustion engine. Thenature of the engagement between an engine 44 and heater 1 may be by anymeans selected with good engineering judgment.

In embodiments in which engine 44 is an internal combustion engine itmay be adapted to generate work from the combustion of any of a largevariety of fuels, including, but not limited to, diesel fuel oil,another suitable grade fuel oil, kerosene, gasoline, propane, naturalgas, alcohol, or the like. In certain embodiments, engine 44 may beadapted to use the same fuel 20 as heater 1 and may be supplied withfuel from fuel tank 3. In certain embodiments, engine 44 may be adaptedto use a fuel supplied from a one pound, or twenty pound, or other sizepropane bottle.

In embodiments in which engine 44 is an external combustion engine itmay be a Stirling engine, an Ericsson engine or any other kind ofexternal combustion engine. In embodiments in which engine 44 is anexternal combustion engine it may be adapted to generate work from heatgenerated by heater 1. In order to receive sufficient heat from heater 1to generate a desired amount of work, an external combustion engine maybe engaged proximate to the combustion chamber 10, or proximate to theshell 12, or proximate to the baffle 13.

Certain embodiments of the present subject matter utilize the air forcedinto the combustion chamber 10 by the fan blades 18 to draw fuel fromthe fuel tank 3 into the combustion chamber 10. According to theseembodiments, the air is directed passed the nozzle 36, thereby creatinga vacuum force that draws the fuel from the fuel tank 3 and directs itinto the combustion chamber 10.

When AC electric energy from an external source is unavailable, therectifier 58 can conduct DC electric energy from the power source 24 viaa conductive pathway 64 to the control unit 62. Since rectification ofthe DC electric energy from the power source 24 is not needed if DCelectric energy is demanded, the rectifier 58 can merely establish theconductive pathway 64 leading to the control unit. In response to acontrol command input by the operator, the control unit 62 canselectively establish and break conductive pathways corresponding to thecontrol command to activate and deactivate the appropriate electriccomponent(s) of the heater 1.

While in some embodiments, motor 15 is adapted to be energized by DCelectric energy, in certain embodiments, the heater 1 can optionallyinclude a motor 15 or other electric load component that is adapted tobe energized by AC electric energy. For such embodiments, if the powersource 24 is a battery, thermoelectric component 32, generator 43 orother source of electric energy adapted to provide DC electric energy,the heater 1 can further include an inverter 66 to convert the DCelectric energy into AC electric energy to be utilized by the motor 15or other component. When an external source of AC electric energy suchas a wall outlet or generator is available, the rectifier 58 can conductthe AC electric energy via a conductive pathway to the control unit 62without rectifying it into DC electric energy. Thus, the AC electricenergy conducted by the plug 28 from the external source is conducted tothe control unit 62 as AC electric energy for use in energizing one ormore AC electric load components corresponding to a control commandinput by the operator via switch 42, control panel 46, and the like.Additionally, if an external source of AC electric energy is available,the rectifier 58 can simultaneously rectify the AC electric energy intoDC electric energy for charging the battery or other such power source24. In certain embodiments, electrical energy provided from athermoelectric component 32 or a generator 43, may be used for charginga battery or other power source 24.

If the heater 1 includes one or more electric load components to beenergized with AC electric energy and such electric energy is notavailable from an external source of AC electric energy, an inverter 66may convert DC electric energy from the power source 24 into AC electricenergy. This inverted AC electric energy is conducted by a conductivepathway 68 to the control unit 62, which establishes one or moreconductive pathways to the component(s) to be energized with AC electricenergy corresponding to the control command input via switch 42, controlpanel 46, and the like.

The embodiment of the heater 1 shown in FIGS. 1 and 2 further includesan optional electric energy outlet 81 into which external electric loadaccessories such as radios, clocks, power tools and the like can beplugged. The outlet 81 includes one or more female receptacles 83 thatcan receive conventional two-prong electric power cord plugs.Accordingly, each receptacle 83 includes at least two apertures 85 intowhich the prongs of the plug provided to the external electric loadaccessory are inserted to establish an electrical connection between theheater 1 and the external electric load accessory.

The outlet 81 can act as a source of AC electric energy to energize anexternal electric load accessory when a conventional wall outlet orgenerator is not available. The outlet 81 can also act as an extensionof a conventional wall outlet or generator when such an external sourceof AC electric energy is available.

When an external source of AC electric energy is unavailable, theinverter 66 may convert DC electric energy from the power source 24 intoAC electric energy. The AC electric energy output by the inverter 66 canbe in the form of a sinusoid having a peak in the form of a with a peakvoltage of about 170 volts and a frequency of about 60 Hz, similar tothe AC electric energy sourced by a conventional wall outlet. However,it should be noted that the AC electric energy output by the inverter 66can deviate from a perfect sinusoid, and in fact, can take on the shapeof a square wave, triangular waveform, and any other waveform shapesuitable for energizing an external electric load accessory. Due to thelarge power output capacity of a battery, such as the lithium ionbattery described above, some of which can output up to 3000 Watts, theexternal electric load accessory can be energized by AC electric energyconverted from DC electric energy supplied by the battery or other powersource 24.

When an external source of AC electric energy is available to the heater1, the rectifier 58 can conduct the AC electric from the external sourceto the control unit 62. The control unit 62 is operatively connected tothe one or more electrical outlets 81 to establish a conductive paththere between. Thus, in addition to controlling the flow of any ACelectric energy required to energize one or more components of theheater 1, the control unit 62 can also direct the AC electric energy tothe outlet 81. Even when the heater 1 is not combusting the air/fuelmixture to deliver thermal energy to the ambient environment of theheater 1, the outlet 81 can still be utilized by an external electricload accessory. This is true regardless of whether the AC electricenergy is converted from DC electric energy from the power source 24 orsupplied from a conventional wall outlet, generator or the like throughthe heater's plug 28.

The control unit 62 may operate in conjunction with a power source 24 arectifier 58, an inverter 66, other power conditioning equipment, or acombination thereof, to accept, condition, process, convert, storeand/or use electrical energy from an external source of AC electricenergy that deviates substantially from the AC electric energyconventionally provided in the United States. For example, and withoutlimitation, in some world regions, it is common for AC electrical energyto be provided at 220v and/or 50 Hz. The heater 1 may be adapted toaccept AC electrical energy having any voltage within a range ofvoltages, and having any frequency within a range of frequencies. Forexample and without limitation, the heater 1 may be adapted to accept ACelectrical energy having a voltage ranging from 0 to 240 volts, and/or afrequency ranging from 50 to 60 Hz.

The outlet 81 may be any of the conventional outlet varieties commonlyused in the United States, or may be any other type of outlet, such as,without limitation, a conventional 12v DC outlet, or any of theconventional outlet varieties commonly used in Japan, Europe, GreatBritain, China, Israel, India, or elsewhere. Control unit 62 may operatein conjunction with a power source 24 a rectifier 58, an inverter 66,other power conditioning equipment, or a combination thereof, to outputto outlet 81 electrical energy that is DC or that is AC electric energy.In certain embodiments, the properties of the electric energy output tooutlet 81 may be selectable by a operator such that a operator mayselect DC electrical energy, or AC electrical energy having any voltagewithin a range of voltages, and having any frequency within a range offrequencies. For example and without limitation, the heater 1 may beadapted to output to outlet 81 AC electrical energy having a voltageranging from 0 to 240 volts, and/or a frequency ranging from 50 to 60Hz.

Thus, the power source 24 provided to the heater 1 can selectivelysupply electric energy, AC, DC, or any combination thereof to one ormore of the following electric load components of the heater 1: anigniter such as a hot surface igniter, spark igniter, and the like; afan; a blower; one or more electric outlets 81; one or more lights 38; athermostat; and any combination thereof. Further, the power source 24can supply this electric energy simultaneously while combustion of thecombustible fuel is taking place, or in the absence of the combustion ofthe combustible fuel. Electric energy supplied by the power source 24can be supplied at least temporarily in the absence of an externalsource of electric energy, simultaneously with the supply of electricenergy from an external source, or as a backup power supply.

An alternate embodiment of a forced-air heater 110 according to thepresent subject matter is shown in FIG. 5. The embodiment in FIG. 5, incombination with one or more of the features discussed above, canoptionally further include a chassis that facilitates mobility of theheater 110, and the ability to be stored in a substantially-verticalorientation with only minimal, if any, leakage of the liquid fuel fromthe fuel tank 114. One or more wheels 124 can optionally be provided tofacilitate transportation of the forced-air heater 110. Each wheel 124can include a rim 126 provided with a rubberized exterior coating 128about its exterior periphery. According to an embodiment of theforced-air heater 110, the fuel tank 114 includes agenerally-cylindrical passage formed in the housing through which anaxle extends to support the wheels 124. Each wheel 124 can alsooptionally be positioned within a wheel well 130 formed in the fuel tank114. The wheel wells 130 allow the wheels 124 to be recessed inwardlytoward the center of a fuel tank 114 thereby giving the forced-air 110 agenerally-streamlined configuration.

A frame 132 fabricated from an arrangement of tubes or rods made from ametal or other suitably-strong material for supporting the weight of afully fueled forced-air heater 110 forms a cage that at least partiallyencases the heating conduit 112 and fuel tank 114. The frame 132includes a proximate end 134 and a distal end 136 separated bylongitudinally extending members 138. A cross member 140 can serve as ahandle at the proximate end 134, allowing the operator to grasp theforced-air heater 110 and maneuver it as desired. A member 138′ canextend longitudinally along each side of the forced-air heater 110adjacent to the fuel tank 114 and externally of the wheels 124. In thisarrangement, the member 138′ allows for simplified installation of thewheels 124 and the frame 132, and also protects the wheels 124 fromimpacting nearby objects while the forced-air heater 110 is beingmaneuvered.

FIG. 6 illustrates transportation of the forced-air heater 110 in asomewhat vertical orientation according to an embodiment of the presentsubject matter. The orientation of the forced-air heater 110 shown inFIG. 6 is but one of the possible orientations in which the forced-airheater 110 can be oriented without leaking significant amounts of liquidfuel from the fuel tank 114. This orientation is an example of what ismeant herein by references to an orientation other than the orientationin which the forced-air heater 110 is intended to be fired, which is theorientation shown in FIG. 5.

FIG. 7 illustrates an embodiment of a forced-air heater 110 in asubstantially-vertical storage orientation. When not in use, theforced-air heater 110 can be stood on the distal end 136 of the frame132. The tubing made from a metal or other strong material that formsthe distal end 136 of the frame 132 is patterned to give the distal end136 a suitably-wide footprint that can maintain the forced-air heater110 in the substantially vertical orientation shown in FIG. 3. Thefootprint of the distal end 136 can optionally be large enough tomaintain the substantially-vertical orientation of the forced-air heater110 even when minor forces are imparted on the forced-air heater 110above the distal end 136 with reference to FIG. 7.

While the forced-air heater 110 is in the substantially-vertical storageorientation, a rain shield 142 is positioned to interfere with the entryof falling objects or other debris into the heating conduit 112. Therain shield 142 can be a planar sheet of metal or other rigid materialthat extends between the cross member 140 that serves as the handle anda second cross member 144. With the rain shield 142 positioned as shownin FIG. 7, it interferes with the entry of falling objects into the endof the heating conduit 112 in which air is drawn from the ambientenvironment.

The forced-air heater 110 has been described thus far and illustrated inthe drawings as optionally including a rain shield 142 adjacent to theambient air intake end of the heating conduit 112. However, it is to benoted that the present subject matter is not limited solely to such anarrangement. Instead, the present subject matter also encompasses aforced-air heater 110 that can be stored in a substantially-verticalorientation such that the discharge end of the heating conduit 112 fromwhich heated air is forced is aimed upwardly, and the ambient air intakeend is aimed toward the ground. Of course, the fuel-management system ofthe present subject matter described below will be adapted accordingly.

FIG. 8 is a cross-section view of an embodiment of a fuel tank 114,which forms a portion of the combustion heater's fuel-management system.The fuel tank 114 includes one or more cavities 146 that alternatelyaccommodates liquid fuel and an air gap that is shifted when theforced-air heater 110 is transitioned from its firing orientation (shownin FIG. 5) to its substantially-vertical storage orientation (shown inFIG. 7), and vice versa. A fuel outlet 154 is provided adjacent to thelowermost portion of the fuel tank 114 while the forced-air heater 110is in its horizontal firing position. Positioning the fuel outlet 154 inthis manner allows approximately all of the fuel to be removed from thefuel tank 14 during operation of the forced-air heater 110.

A hose 158 is connected between the fuel outlet 154 and a nozzle 160through which the fuel is metered into the combustion chamber 120. Thehose 158 can be fabricated from any material that will resist damage anddegradation from exposure to the particular fuel used to fire theforced-air heater 110. Examples of the types of fuels the hose 158 willtransport include, but are not limited to, diesel fuel oil, anothersuitable grade fuel oil, kerosene, gasoline, alcohol, or the like.

The hose 158 includes an arcuate portion 162, which is also referred toherein as a return curve 162. The return curve 162 is positioned on theforced-air heater 110 such that the return curve 162 is oriented similarto a “U” while the forced-air heater 110 is in itssubstantially-vertical storage orientation, with both arms aimedupwardly in a direction generally opposing the acceleration of gravity.

The location of the fuel inlet 148 through which liquid fuel can beinserted into the fuel tank 114 limits the amount of fuel that can beplaced in the fuel tank 114. With the forced-air heater 110 in itsfiring orientation, the lowest point of the fuel inlet 148 marks theupper fuel level limit 150. Thus, the air gap 152 a is disposed abovethe upper fuel level limit 50 and the liquid fuel in the fuel tank 14.When the forced-air heater 110 is transitioned to thesubstantially-vertical storage orientation shown in FIG. 3, the fuel inthe fuel tank 114 shifts to position an air gap 152 b adjacent to thefuel outlet 154. An example of a suitable size for the air gaps 152 a,152 b is about 0.4 gallons with the fuel tank 114 at its maximumcapacity, but air gaps 152 a, 152 b of any size is within the scope ofthe present subject matter.

The shifting of the fuel in the fuel tank 14 when the forced-air heater110 is transitioned from the intended firing orientation to thesubstantially-vertical storage orientation creates a vacuum at the fueloutlet 154. The vacuum results in the siphoning of fuel from the hose158 back into the fuel tank 114 instead of allowing the fuel to leakfrom the nozzle 160. Additionally, most, if not all of the remainingfuel not siphoned back into the fuel tank 114 is allowed to pool in thereturn curve 162 in the hose 158 instead of draining from the nozzle160. This further minimizes leakage of the fuel from the forced-airheater 110.

Although much of the description above focuses on portable forced-airheaters, fixed heating installations such as furnaces are also withinthe scope of the present subject matter.

Illustrative embodiments have been described, hereinabove. It will beapparent to those skilled in the art that the above devices and methodsmay incorporate changes and modifications without departing from thegeneral scope of this subject matter. It is intended to include all suchmodifications and alterations in so far as they come within the scope ofthe appended claims.

1. A forced-air heater comprising: a self-contained on-boardelectric-power supply comprising, a generator, a photovoltaic component,or some combination thereof; a fuel tank adapted to store a first fuel;a support; a housing; a combustion chamber adapted to generate heat bycombusting the first fuel with air; and a motorized fan adapted tooperate to, draw in ambient air through an air intake, and force the airinto the combustion chamber.
 2. The forced-air heater of claim 1,wherein said self-contained on-board electric-power supply comprises aphotovoltaic component.
 3. The forced-air heater of claim 2, furthercomprising a battery.
 4. The forced-air heater of claim 3, wherein thebattery is a lithium ion battery or a sealed lead-acid battery.
 5. Theforced-air heater of claim 1, wherein said self-contained on-boardelectric-power supply comprises a generator.
 6. The forced-air heater ofclaim 5, further comprising an engine operationally engaged with thegenerator.
 7. The forced-air heater of claim 6, wherein the engine is anexternal combustion engine.
 8. The forced-air heater of claim 7, whereinthe engine is adapted to generate work from the heat.
 9. The forced-airheater of claim 6, wherein the engine is an internal combustion engine.10. The forced-air heater of claim 9, wherein the engine is adapted togenerate work from combustion of a second fuel.
 11. The forced-airheater of claim 10, wherein said second fuel is a fuel oil, kerosene,gasoline, propane, natural gas, or alcohol.
 12. The forced-air heater ofclaim 11, wherein said second fuel is a different fuel from said firstfuel.
 13. The forced-air heater of claim 10, wherein said second fuel isa fuel oil, kerosene, gasoline, or alcohol.
 14. The forced-air heater ofclaim 13, wherein said second fuel is the same fuel as said first fuel.15. A method for producing heat, comprising providing a forced-airheater, said forced-air heater comprising: a self-contained on-boardelectric-power supply comprising, a generator, a photovoltaic component,or some combination thereof; a fuel tank adapted to store a first fuel;a support; a housing; a combustion chamber adapted to generate heat bycombusting the first fuel with air, a motorized fan adapted to operateto, draw in ambient air through an air intake, and force the air intothe combustion chamber; generating electric power from saidself-contained on-board electric-power supply; and directing a majorityof said generated electric power to an electric load component orexternal electric load accessory other than a resistive heating element.16. The method of claim 15, wherein said self-contained on-boardelectric-power supply comprises a photovoltaic component.
 17. The methodof claim 15, wherein said self-contained on-board electric-power supplycomprises a generator.
 18. The method of claim 17, further comprising anengine operationally engaged with the generator.
 19. The method of claim18, wherein the engine is an internal combustion engine adapted togenerate work from combustion of a second fuel different fuel from saidfirst fuel.
 20. A forced-air heater comprising: a self-containedon-board electric-power supply comprising a generator; a fuel tankadapted to store a first fuel, said first fuel comprising fuel oil,kerosene, gasoline, or alcohol; a support; a housing; a batterycomprising a lithium ion battery, or a sealed lead-acid battery; anengine operationally engaged with the generator, said engine being aninternal combustion engine adapted to generate work from combustion of asecond fuel other than the first fuel; a combustion chamber adapted togenerate heat by combusting the first fuel with air; a motorized fanadapted to operate to, draw in ambient air through an air intake, andforce air into the combustion chamber.